1. Field of the Invention
The present invention relates to compatible ternary polymer mixtures comprising polycarbonate polymers, polyalkylene terephthalate polymers, and methacrylate copolymers, which mixtures are compatible with polyesters and with polycarbonate.
2. Discussion of the Background
The modification of plastics of the polycarbonate (PC), polyester (PE), and polyester carbonate type, to render them impact resistant is well known (U.S. Pat. No. 4,906,699). Such modified plastics are used as molding compounds, e.g. for injection molding of parts for housings, bumpers, etc. Modifying-agents with a core-and-shell structure have proved particularly effective.
For polyesters, polymeric core-and-shell modifiers have been employed having core material comprised of alkyl acrylate and shell material comprised of alkyl methacrylates and/or styrene copolymers.
For addition to polycarbonates, ABS copolymers, or acrylate modifiers have been used, preferably with styrene-acrylonitrile copolymers in the outermost graft shell.
There are also on the market blends comprised of polycarbonate and polybutylene terephthalate, containing acrylate modifiers, wherein the core of the modifier comprises butyl acrylate and the shell comprises methyl methacrylate and/or styrene-acrylonitrile copolymers.
Compatible blends comprising polyesters and polyaryl acrylates are proposed in unpublished DE-40 03 088.1.
The principal claimed subject matter of EP 297,285 comprises transparent thermoplastically processible binary polymer mixtures comprised of polycarbonates and of methacrylate copolymers, wherein the methacrylate copolymers are comprised of the following:
95-5 wt. % of methyl methacrylate, and
5-95 wt. % of (meth)acrylate esters with cyclic groups in the ester moiety.
Not withstanding the few successes in producing transparent thermoplastic compositions, technical experience with mixtures comprised of disparate polymers was summarized relatively early with the statement, "Miscibility is the exception, immiscibility is the rule" (see Kirk-Othmer, 1982, "Encyclopedia of Chemical Technology", 3rd Ed., pub. J. Wiley, Vol. 18, p. 460). Despite a growing number of counter-examples discovered in recent years, the above statement is characterizing experience in this area of technology which still represents the expectations of those skilled in the art.
It is not by chance that interest in compatible polymer mixtures has grown recently. As a rule, compatible polymer mixtures have the advantage of being transparent. To the extent they are comprised of thermoplastics, they generally have good thermoplastic processibility. In addition, they frequently open up new possibilities for reusability and recycling.
Due to the uniform composition, the mechanical properties are generally adjustable, reproducible, and quite advantageous. However, the prospect of obtaining industrially usable compatible polymer mixtures in ternary mixed systems must be deemed unfavorable.